A layer of sheet material, such as insulation or roofing membrane is commonly attached to a roof or deck or other large surface of a building structure by means of a series of spaced, fastener structures. Typically the fastener structures each consists of a washer-like disk with a fastener such as a screw or nail extending through the disk, the surface layer and into the underlying layer.
In a typical installation procedure, after the surface layer to be attached to the underlying layer is first laid out upon the underlying layer, a first person carrying a supply of the disks walks along and positions them at spaced intervals in the places where they are to be installed. A second person follows behind with a hammer and a supply of screws. The second person pounds the screw through the disk and the suface layer until it strikes the underlying layer. A third man follows the second with a power screwdriver or screw gun and drives the screws into the underlying layer to clamp each disk down against the surface layer and hold it against the underlying layer. This procedure requires several manual operations and therefore is both expensive and slow.
A currently available prior art machine which attempts to automate this procedure is an apparatus having four wheels so it can be pushed along on the surface layer. The screws are fed into the machine in a belt like a cartridge belt used with automatic machine guns. This prior art machine also has a revolving plate which receives a disk in an aperature of the plate and moves it to the position at which a screw driving mechanism attached to the machine installs a screw through the disk. The screwdriver and the revolving plate are synchronized by drive mechanisms so that the automatic screw driver passes through the aperature as it drives a screw through the disk.
In addition to the complexity, size and expense of the prior art device, one particular difficulty which has been experienced occurs when a need arises to remove a screw which did not attach correctly. Occasionally it becomes necessary to back off such a screw with the screwdriver mechanism to remove it. Unfortunately, however, the synchronized drive mechanism attempts to return the revolving plate back to receive another disk as the screwdriver is backed off causing the screwdriver and the plate to interfere and resulting in damage to the plate. Such plates are expensive to replace and such a failure in the equipment causes a substantial time delay for replacement.
There is, therefore, a need for an automatic fastening machine which can position the disks securely and reliably in a position which is both away from potential interference with moving mechanisms and suitable for application of an automatic screw gun to the screw.
Yet another difficulty with machines of this type arises when they are used to apply a roofing membrane and are rolled along the membrane from one fastener position to the next. The action of the wheels upon the membrane causes the membrane to gather and wrinkle. There is, therefore, a need for an automatic fastening machine which can be easily transported along a membrane from each fastener position to the next fastener position without causing such wrinkling.
Yet another disadvantage which arises with this prior art machine apparently occurs because of the need to push the fastener screw out of its carrying belt. In order to do that, the designers of the prior art machine designed it to use hexagonally headed screws. However, the philips head screw is conventional in the roofing industry. One major advantage of the present invention is that it can use philips head screws. It can also use a conventional stand-up screw gun and with slight size modifications any other automtic screw driver or even a manual screw system.
Yet another difficulty with the prior art machine is that it will not work with round disks or with disks with a deeply embossed pattern upon them for additional strength. There is, therefore, a need for an automatic fastening machine which can be utilized with any of the disks which are conventionally available and requires only minor modification needed to the machine for accomodating the various disks.